Electric valve circuit



Feb. 27, 1940. 5,1. REMSCHE ID 2,192,052

ELECTRIC VALVE CIRCUIT Filed D60. 21, 193? Inventor: Emil J. Rerhscheid,

Walt/176 JWAM,

Has Attorney.

Patented Feb. 27, 1940 UNITED STATES.

OFFICE? Wer m.

Emil J. Remscheid, Scotia,.N. Y assignor to eneral Electricv Company, acorporation of New 7 Application December 21, 193s. Serial No. 247,060 7Claims. (01. 175-363) My invention relates to electric valve circuitsand more particularly to deionization circuits for electric valveapparatus employing ionizable me-i diums.

5" Where electric valve means employingioniza-- ble mediums are used inelectric translatingapparatus, it is frequently desirable to providedeionization circuits for collecting the positive ions at the end of thenormal intervals of conduction. 10 Heretofore, the prior artarrangements for effecting deionization of electric valves have beenrelatively complicated in nature and construe-I tion and requiredconsiderable inspectionand maintenance. In accordance with the teachings1-5" of my invention described hereinafter; lE-pro'vide a new andimproved deionization circuit for electric valve apparatus which issimple in construction and operation and which offers additionaladvantages electric valve performance.

go- It is an object of my'inventio'n to provide a new andimprovedelectric valve circuit."

It is another object of my invention towprovide a new and improveddeionization circuit for elec-' tric valve apparatus employing an'ionizable me- 25- dium.

It is a further object of my inventionfto provide a new and improveddeionization circuit for electric valve apparatus of the typeemploying amercury pool cathode and an associatedimmer 3( sion-ignitor controlmember.

v In accordance with an illustrated embodiment of my invention, Iprovide a new and improved control circuit for electric valve apparatus.Electric valve means of the type employing an ioniza'-' ble medium isconnected between an alternating current supply circuit and a directcurrentload circuit. The electric valve means is of thetype employingmercury vapor as an ionizablemedium and'the electric valve meanscomprises an anode,

0'; a mercury pool cathode and an immersion-ignitor control memberassociated with the cathode.

An auxiliary electrode or baflle is placedin the vicinity of the anodeand is permanently connected to the anode through an energy con-- 3suming means such as a resistance. The resistance and the auxiliaryelectrode constitute a deionization circuit for theelectric valve means.In one embodiment of my invention, a control or excitation circuit isconnected between the, im- 50 mersion-ignitor control member and thecommon juncture of the resistance and'the auxiliary electrode andenergizes the control member to render the electric valve meansconductive b-y'the conduction of unidirectional current to the con-;tr01 memben' The' control circuit comprises an appended claims. Figs. 1and 2 of the drawing diagra'rrimatically illustrate embodiments of myinvention as applied to electric valve translating apparatus fortransmitting power between an 15" alternating currentcircuit and adirect current circuit. I r

' "In Fig. 1 of the accompanying drawing, I have diagrammaticallyillustrated my invention as applied to an electric valve translatingcircuit for 20* transmitting'power between an alternatingcurrent circuitl and a direct current circuit 2 through a transformer 3 having aplurality of primary windings 4 and a plurality of groups of secondarywindings 5 and 6. An interphase 2 5 transformer l connects the'groups ofsecondary windings 5 and 6 toone terminal of the direct, currentcircuitZ. The translating apparatus also comprises a plurality ofelectric valve means 8-|3-, inclusive; {which areof the type employing36 an ioniz'able medium such as a gas or a vapor. For the purposes ofillustration, the electric valve means il -l3 are shown as being of thetype employing-a self-reconstructingcathode l4 such asa mercury pool, ananode l5, and a control member l6 which -may be of the immersion,ignitor type having an extremity immersed in the mercury; of the cathodeM. The immersionignitor' controlmember l6 of each of the electric valvesispreferably constructed of a material '0 having anelectricalresistivity which is relatively great with respect to that ofthe associated mercury pool cathode. The immersion-ignitor controlmember It may be constructed of a poorly 'conducting'or.semi-conductingmaterial such as '5 boron-carbide or silicon-carbide. Each of theelectric valve means 8-l3 is provided with an auxiliary electrode orbaflle I! which isplaced in the vicinity of the associated anode l5 andwhich maysubstantially surround the anode IS. The 56- auxiliaryelectrode l'l may be constructed of graphite and may be perforated; andthe number and the size of the perforations are designed to control theeffect of the auxiliary electrode on the associated anode l5. I providea plurality 5 s 25 in order to control the magnitude of the ourofdeionization circuits l8-23 associated with the electric valve means8-!3, respectively. Each of the deionization circuits is responsive tothe anode voltage or to the polarity of the anode voltage of theassociated electric valve means and is permanently connected to theanode and comprises a suitable energy absorbing means, such as aresistance 24, which serves to absorb the energy incident to thedeionization of the mercury vapor 0f the associated electric valve meansafter the normal interval of conduction for that electric valve means.

when the value of the resistance 24 is 500 ohms; this value ofresistance has proved to be a critical value for the particular electricvalves in which the invention has been embodied.

I also provide a plurality of control or excita: tion circuits 25 eachassociated with a diiferent one of the electric valve means 8-43. Forthe purpose of illustration, only excitation circuit 25 associated withelectric valve means 8 is shown. Each of the control circuits 25 isconnected between the immersion-ignitor control member l6 oi theassociated electric valve means and a common juncture 26 of theassociated auxiliary electrode H and the resistance 24, The controlcircuit 25 effects energization of the immersionignitor control memberIE to render the electric valve means conductive in a predeterminedorder and at predetermined times during the cycle of appliedanode-cathode voltage. Each of the control circuits 25 may comprise asuitable electronic discharge device 21 which is preferably of the typeemploying an ionizable medium, such as a gas or avapor, and which maycomprise a 1 control member or grid 28 Which renders the electronicdischarge device 21 conductive to efiect energization of theimmersion-i'gnitor conitrol member I6 at a predetermined time during thecycle of applied anode-cathode voltage of the associated electric valvemeans. A current controlling or limiting resistance 29 may be con-,nected in series relation with the electronic discharge device 2'! ineach of the control circuits rent transmitted to the associatedimmersionignitor control member l6. The input circuits of the electronicdischarge devices 2'! of the control circuits 25 may be energized from asuitable source of periodic voltage correlated in phase and frequencywith respect tothe voltage of the 25. A suitable source of negativeunidirectional biasing potential, such as a battery 33, maybe connectedin circuit with the control grids 28.. Aphase shifting device, such as arotary phase shifter 34, may be interposed between the transformer 30and the alternating current circu itql to control or adjust the phase ofthe periodic voltages impressed on grids 28 of electronic dischargedevices 2'? and hence to control the times during the cycles of appliedanode-cathode voltage, at which the electric valve means 8-l3 arerendered conductive.

The operation of the embodiment of my invention shown. in Fig. '1 of theaccompanying drawing will be explained by considering-the system when itis operating as a rectifier to en- I have'found that the do ionizationcircuits operate very satisfactorily m'ersion-ignitor control memberEach of ergize the direct current circuit 2 from the alternating currentcircuit 1. that the electric valve means 8-43 conduct our- It will be,understood rent in a predetermined order or sequence and that eachelectric valve means conducts current for substantially electricaldegrees; The times during which the electric valve means'B-H arerendered conductive during the respective cycles 'of' appliedanode-cathode voltage determine the magnitude of the voltage applied tothe direct current circuit 2. The electric valves 8-43 are renderedconductive by transmitting to the iml6 a current of predeterminedmagnitude in order to initiate y a cathode spot on the surface of theassociated mercury pool cathode l4 and thereby eifect'ionization'of themercury vapor between the anode I5 and the cathode l4. Thejcontrolcircuits 25 are rendered conductive by the pro-per sequential operationof the control circuitsassociated with grids 28 to transmitunidirectional currents to the immersion-ignitor control members 16. A

By virtue of the improvedv deionization- ,circuit which I provide; Ihavefound that the normal load rating or current ratingnof electric valvemeans of this type may be substantially increased. For example, I havefound that by employing my deionization circuit, the normal load;ratingof the electric valve means is doubled: andthatthe instantaneous ortemporary overload rating is tripled. When the electric valve means=.8--l3 are conductive, current is transmitted between the anode andthecathode by the ionization-of the-mercury vapor. Part-of thecurrenttransmitted is conducted by means of electrons and part isconducted by positive mercury ions. The electrons during the normalperiod f conduction flow toward the anode and the positive ions flowtoward thecathode. As will'be well un-- derstood by those skilled in theart, current is ,commutated among the various electric valve. means 8-13by the sequential change in the voltages impressed on the variousanodes; that is, current is conducted by that electric valve means ofeach group associated withwindings 5 and 6, the anode. of ,whichis morepositive than the anode of any other associated; electric valve means.At the time current is commutated from 1 I an electric valve means andimmediately: thereafter, the mercury vapor of that electricvalve means:is highly ionizedandthe energy due to suchionization must be dissipatedin orderthat the electric valvemeans be restored to'a non-f conductivecondition. Immediately. after commutation, due ,to' the cyclic variation.of the'applied anode-cathode-voltage, .the anode of a particularelectric valve means becomes negativein; 6

potential with respect to the associated cathode.

Under these conditions, the electrons move to.- ward the cathode and thepositive ions move.- The energy, due to the de-. ionization of themedium, is therefore dissipatedtoward the anode.

in thef orm of heat on the cathode and the anode. Due to the relativelylarge number of mercury vapor positive ions, the amount of 'heat gen--e'rat'ed by theimpinging positive ions on the anode is relatively large,causing an appreciable increasein temperature of the anode andanappreciable rise intemperature of the entire electric valve means. ItWill be understood that if the rise in temperature for a particularelectric valve means becomes, suficiently great; the: anode may? ornumber of the positive ions which finallyv tend to operate as a cathodedue to the formation of a cathode spot on the anode caused by theimpinging positive ions.

The deionization circuits [8-23 offer several distinct advantages. Thesecircuits increase the current rating of the electric valve means andalso tend to prevent arc-backs. During the working or positive halfcycles, the auxiliary electrode l1 assumes a potential intermediate thatof the anode and the cathode by virtue of the highresistance electricalconnection to the anode through the resistance 24. During the first partof the inverse half cycle, that is, after the commutation of currentfrom a particular electric valve the auxiliary electrode l1 remains atsubstantially the same potential with respect to the cathode. The dutyimposed on the anode is substantially reduced during the deionizationperiod, since the space which must be deionized by the anode is nowlimited to the space between the anode and the auxiliary electrodes andthe positive ion current is accordingly reduced below that which wouldbe obtained were the auxiliary electrodes not present. Since the ratingof electric valve means of this type is in a measure dependent upon themaximum temperature ofthe electric valve means during the cycle ofoperation, it is to be understood that the presence of the auxiliaryelectrode l1 and the associated deionization circuit increases thecurrent rating of the electric valve means.

The deionization circuits also tend to prevent arc-backs by limiting themaximum temperature of the associated anode. Without attempting arigorous explanation of the mechanism by virtue of which this advantageis obtained, this improved operation may be explained in the followingmanner. One of the most likely theories is that immediately aftercommutation of current from a conducting valve of this type, the mercuryvapor positive ions tend to move toward the anode. The velocity of theseions is determined by the difference in voltage between the anode andthe cathode and the velocity, of course, increases as the ions approachthe anode. If the ions attain a reasonably great velocity and if thenumber of ions is large, there is produced on the surface of the anode acathode spot due to the heat generated by the impinging positive ions.Under such conditions, the anode would tend to operate as a cathode.However, by the use of the auxiliary electrode I! connected inaccordance with the teachings of my invention, that is, by connectingthe auxiliary electrode to the anode through a relatively highresistance, there is provided a path for the dissipation of the energydue to the positive ions whichmigrate toward the anode during thedeionization period. The auxiliary electrode collects the positive ionsmoving toward the anode; and by virtue of the collection of the positiveions, current flows through the resistance 24, and the energy isdissipated in the resistance. Of course, the presence of the auxiliaryelectrode l1 tends to reduce the voltage gradient within the spacebetween the anode and the auxiliary electrode, thereby reducing themigrate to the anode. In addition, the quantity reach the anode issubstantially reduced because the auxiliary electrode is interposedbetween the 1 cathode and the anode.

The temperature of the auxiliary electrode is maintained below thatvalue V which would cause the auxiliary electrode to oplimits themagnitude of the current which can flow due to the deionization of themercury vapor. In this manner, the resistance 24 prohibits thegeneration of an excessive amount of heat on the auxiliary electrode I!by limiting the amount of current which can be conducted from theionized mercury vapor through the auxiliary electrode to the powercircuit during the deionization interval.

Itwill be appreciated that by virtue of my invention there is providedan improved arrangement for effecting deionization of an electric valvemeans of thetype employing an ionizable medium, without sacrificing theefiiciency of the system. Fig. 2 diagrammatically illustrates anotherembodiment of my invention and is a modification of the arrangementshown in Fig. 1; corresponding elements have been assigned likereference numerals. In the arrangement of Fig. 2, the electronicdischarge device 2'! is connected directly to the anode l5 of theassociated electric valve means 8, and the cathode of the electronicdischarge device 2'! is connected to the control member it of theelectric valve means 8. The input circuit of the electronic dischargedevice 21 is connected between the control grid 28 and the commonjuncture of the cathodes of the electric valve means 8-l3; that is, theone terminal of the input circuit is connected to the positive terminalof the direct current circuit 2. The arrangement of Fig. 2 operates insubstantially the same manner as that explained above in connection withFig. 1. At predetermined times, depending upon the phase of the voltageimpressed on the control grid 28, electronic discharge device 2'i isrendered conductive, effecting energization of the immersion-ignitorcontrol member l6 of the associated power electric valve means.Energization of the control member l6 establishes an arc dischargebetween the cathode and the anode, rendering the principal electricvalve means conductive. The deionization circuit including theresistance 24 absorbs'the energy due to the deionization of the mercuryvapor, effecting an increase in the current rating of the electric valvemeans and tending to prevent arcbacks.

While I have shown and described my invention as applied to a particularsystem of connections and as embodying various devicesdiagrammaticallyshown, it will be obvious to those skilled in the artthat changes and modifications may be made without departing from myinvention, and I, therefore, aim in the appended claims to cover allsuch changes and modifications as fall within the true spirit and scopeof my invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. In combination, an alternating current circuit, a load circuit,electric translating apparatus connected between said circuits andcomprising electric valve means employing an ionizable medium and havingan anode, a cathode, a control member of the immersion-ignitor type andan auxiliary electrode in the vicinity of said anode, a control circuitresponsive to the voltage of said anode and comprising an electronicdischarge device for effecting energization of said control member torender said electric. valve means conductive, and a deionization circuitconnected to said auxiliary electrode and being responsive to thevoltage of said anode.

2. In combination, an alternating current circuit, a load circuit,electric translating apparatus connected between said circuits andcomprising electric valve means employing an ionizable medium and havingan anode, a cathode, a control member of the immersion-ignitor type andan auxiliary electrode in the vicinity of said anode, a control circuitconnected between said anode and said control member and comprising aunidirectional conducting device responsive to the voltage of said anodefor efiecting energization of said control member to render saidelectric valve means conductive, and a deionization Circuit connectedbetween said control circuit and said auxiliary electrode.

3. In combination, an alternating current circuit, a load circuit,electric translating apparatus connected between said circuits andcomprising electric valve meansemploying an ionizable medium and havingan anode, a cathode, a control member of the immersion-ignitor type andan auxiliary electrode in the vicinity of said anode, a control circuitresponsive to the polarity of the voltage of said anode and comprising aunidirectional conducting device for transmitting unidirectional currentto said control member to render said electric valve means conductive,and a deionization circuit connected to said auxiliary electrode andbeing responsive to the voltage of said anode and comprising an energyconsuming means for dissipating energy incident to the deionization ofsaid medium.

4. In combination, an alternating current circuit, a load circuit,electric translating apparatus connected between said circuits andcomprising electric valve means employing an ionizable medium and havingan anode, a cathode, a control member and an auxiliary electrode in thevicinity of said anode, a resistance connected between said anode andsaid auxiliary electrode, and a control circuit for energizing saidcontrol member and being connected between said control member and thecommon juncture of said resistance and said auxiliary electrode.

5. In combination, an alternating current circuit, a load circuit,electric translating apparatus connected between said circuits andcomprising electric valve means employing an ionizable medium and havingan anode, a cathode, a control member of the immersion-ignitor type andan auxiliary electrode in the vicinity of said anode,

a control circuit comprising an electronic dis,

charge device responsive. to the polarity of the voltage of said anodefor effecting energization of said control electrode to render saidelectric valve means conductive by initiating an are discharge betweensaid cathode and said anode, and a resistance connected between saidanode and said auxiliary electrode for dissipating the energy incidentto the deionization of said medium when said anode becomes negative inpotential with respect to said cathode after the normal interval ofconduction of said electric valve means.

6. In combination, an alternating current circuit, a load circuit,electric translating apparatus connected between said circuits andcomprising electric valve means employing an ionizable medium and havingan anode, a cathode, a control member and an auxiliary electrode in thevicinity of said anode, a deionization circuit comprising a resistanceconnected between said anode and said auxiliary electrode, and a controlcircuit connected between the common juncture of said resistance andsaid auxiliary electrode and said control member and comprising anelectronic dischargedevice for transmitting unidirectional current tosaid control member to render said electric valve means conductive.

7. In combination, an alternating current circuit, a load circuit,electric translating apparatus connected between said circuits andcomprising electric valve means employing an ionizable met dium andhaving an anode, a cathode, a control member and an auxiliary electrodein the vicinity of said anode, a deionization circuit comprising aresistance connected between said anode and said auxiliary electrode, acontrol circuit connected between the common juncture of said resistanceand said auxiliary electrode and said control member and comprising anelectronic disclrarge device for transmitting unidirectional current tosaid control member to render said electric valve means conductive andmeans for controlling the conductivity of said electronic 7 dischargedevice.'

ElVllL J. REMSCHEID.

